http://dspace-su.server.ly:8080/xmlui/handle/123456789/485 2026-05-03T12:59:02Z http://dspace-su.server.ly:8080/xmlui/handle/123456789/571 The Flow Characteristics and Thermal Performance of Nanofluid in a Vertical Microchannel: A numerical study Saleh Etaig; Gamal Hashem Electronic cooling remains a challenge that requires further research and investigation due to the ever-higher heat flux. Microchannels are one of several high heat flux heat dissipation designs that meet this requirement. Nanofluids exhibit not only dramatically improved thermal conductivity, but also thermophysical properties that are strongly temperature- and size-dependent, which can be achieved by adding nanoparticles with diameters less than 100 nm to conventional liquid working fluids. increase. Nanofluids are expected to be used as coolants in microchannel heat sinks to achieve a double benefit in improving heat transfer and to meet the increasing cooling demands of electronic devices. The present work focus on the flow characteristics and enhancement of heat transfer in a vertical microchannel with a triangular microchannel using magnesium oxide water nanofluid. A wide range of volume fractions was tested in this work, the governing equations were solved using the finite volume technique. An external heat flux was applied on the three walls. The three-dimensional analysis showed that the increase in the volume fraction promoted the heat transfer remarkably, the water base fluid showed the lowest Nu number along the microchannel wall, while no penalty for the pressure drop was achieved with the increase in the volume fraction. 2022-01-01T00:00:00Z http://dspace-su.server.ly:8080/xmlui/handle/123456789/569 Identification of Gas Void Fraction and Flow Patterns in Upward Direction of Vertical Pipes Almabrok A. Almabrok; Faraj A. AlTaher Experiments on gas-liquid two-phase flow were conducted at three positions of upward section in a vertical pipe with diameter of 101.6 mm. In this study, probability density functions (PDFs) and local distribution of gas void fraction were applied to identify the possible flow patterns that can be formed in a vertical upward orientation. It was observed from the shape of PDFs that bubbly, intermittent and annular flows are the dominant types. These flow structures were significantly influenced by gas and liquid superficial velocities. Bubbly flow was formed at low gas flowrates, which was characterized by discrete bubbles distributed in a liquid continuum. The bubbles were uniformly distributed in the pipe center with similar shape and size. Intermittent flow was formed due to gradual increase of gas flowrate, where large bubbles tend to collide and coalesce with the smaller ones. The bubbles are noted to occupy the greater part of the pipe's cross-section. Fluctuations of gas flowrate led to distortion and breakdown of the large bubbles immediately. Further increase of gas flowrate was attributed to formation of annular flow regime. In this type, the liquid phase flows along the pipe walls in the form of liquid film, while the gas phase flows in the center of the pipe. Further attempts were also performed by examining the local distribution of gas void fraction which confirmed the achieved above-mentioned results. 2022-01-01T00:00:00Z http://dspace-su.server.ly:8080/xmlui/handle/123456789/566 Application of Genetic Algorithms to Estimate Preventive Maintenance Interval: A Pump Device as a Case Study Abdelnaser Elwerfalli; Faraj Altaher; Salih Alsadaie Genetic Algorithms is one of the techniques which has been applied in recent years to contribute to the scheduling of Preventive Maintenance (PM) to improve the whole system performance and run efficiently and effectively. This paper aims to estimate the interval of preventive maintenance for any processing equipment using genetic algorithms. A centrifugal pump is presented as critical equipment to apply a genetic algorithm to prolong the interval of PM. The obtained results show that a genetic algorithm is effective and practical in estimating the optimum time of preventive maintenance for centrifugal pumps 2022-01-01T00:00:00Z http://dspace-su.server.ly:8080/xmlui/handle/123456789/563 Use of Tefla as Partial Replacement of Cement in Concrete Mix Abraheem S. Alhireer; Hamza Ben Omran Abundant is tefla (Yellow Tefla, Green Tefla) in OmAlrozam, a town near the city of Derna, Libya. Cement is one of the components of concrete plays a great role in the construction industry. Higher consumption of cement in the construction industry leads to higher pollution. To make economic aspects in the construction industry and protecting the environment from pollution and also cement production emits CO2 into the atmosphere which is harmful to nature. If we can partially replace the cement with the material with desirable properties then we can save natural material and reduce the emission of CO2 into the atmosphere. This study aimed to investigate the suitability of using tefla in concrete. The tefla were ground to roughly cement fineness, which has been sieved and passing through 90 microns and after grinding, the chemical composition of the tefla material was determined using X-Ray Fluorescence (XRF). Four replacement levels,5%,10%,15% and 20% with a w/c ratio of 0.50. The workabilities of the fresh concrete mixes were evaluated using the slump test while compressive and splitting tensile strengths of hardened concrete were evaluated at different curing periods of 3, 7, 14 and 28 days, the workability of the concrete reduce with an increase in tefla powder content. Better result in mechanical properties (compressive strength and splitting tensile strength) and physical properties (water absorption and porosity) of the concrete was achieved at 5% cement replacement of yellow tefla, after which a decrease in strength with increasing tefla content was recorded. The use of yellow tefla of not more than 5% was recommended for concrete production 2022-01-01T00:00:00Z